Mars City Underground: Union Aerospace Subsystems/Walkthrough


Doom 3 walkthroughs
Mars City Underground: Union Aerospace Subsystems
Mars City
Alpha Labs
Enpro Plant
Delta Labs
Delta Complex
Central Processing

This is a detailed walkthrough for Mars City Underground: Union Aerospace Subsystems. Your mission is to find the missing scientist Jonathan Ishii and return with him to Sergeant Kelly.


Finding the scientist[edit]

The trip to Jonathan Ishii is a simple follow-the-corridor sequence, though a few items can be found on the way which will make the second half of the level easier. While T. Brooks is speaking with you, he will open one of the two armament cabinets near the entrance elevator; walk up to it to receive a pistol and bullets, flashlight, and some armor. If you took any falling damage during the introductory level, a med kit is also here to relieve it. Once he finishes speaking, he will unlock the door to the Underground Junction and you can proceed onward.

On the way to find the scientist, you will come across several minor characters. The first of these, D. Young, is positioned near the crane controls in the junction. You can shoot him if you are attempting to acquire all PDAs in the game, but otherwise he can be ignored. Proceed down the catwalks to the next door.

Inside the next room, C. Rodgers may surprise you by suddenly calling out - he considers telling you something about the missing scientist that might dissuade you from finding him, but then has second thoughts. It is possible to climb the stack of crates near him and get onto the pipes above this area, where some armor shards are available.

Go through the next small room and then through the subsequent room with large pipes to your right - you will hear R. Fry on the other side of the pipes berating his coworker Scotty, who is down inside a maintenance crawl way. If R. Fry is killed, Scotty will react by asking what is going on out there. Just past them on the left is the first storage cabinet and a PDA for Grant Baston - you can listen to the PDA to find the code for the locker, which is 531. It contains a small med kit, shotgun shells, and some armor shards.

Continue through the next two rooms - any apparent alternate paths are locked for now. You can hear some workers arguing and mentioning frequent power problems in the second room, and in this room you can also jump beside and duck underneath the floor you are walking on to find some more armor shards hidden beneath on the subfloor. In the next room, you will frighten Ian Sinclair as you walk up to him. You can climb down the ladder next to his workstation to find some more armor shards, bullets, and a med kit (you will not likely need it right now) in the area below. Return up top and continue on through the door next to the ladder.

In the next room, the lights will temporarily go out as you descend the stairs to the lower level. Simply walk forward toward the exit door and the power will be restored. Use your flashlight to remain safe.

You have arrived at the surface airlock and will meet Mars Sec guard Mark Ryan, who explains about walking on the surface. He can be killed for a PDA if completion is being sought, but it contains no valuable information. Pick up the bullets next to him and then press the panel on the front of the airlock to open it. Go inside, cycle the airlock, and you will be outside on the Martian surface. You have enough oxygen to walk all the way to the other airlock; if you dawdle, a canister of air is positioned prominently on the bridge.

Once inside the abandoned comms facility, you can find more armor shards and a med kit atop the second shelf, which you can get to by jumping onto a crate below that has been knocked slightly out of place. Open the elevator using the panel to its right, go inside, and select the second floor (Communications) as your destination. When the elevator arrives, go outside and walk along the linear path forward - your first objective is marked as complete. Once you enter the next door, you will meet Jonathan Ishii.

The Hell invasion[edit]

When you meet the scientist, all Hell breaks loose, with Johnathan being transformed into a zombie within a few seconds. Kill him quickly, and turn your attention to the door on the left, watching for the pistol Z-Sec that enters and attacks. You can find more bullets on a console on the left side of the room. Head back to the elevator—a zombie will stumble toward you on the way—and return to the first floor. Upon exiting the elevator, the floor panels will explode and a med kit can be found toward the right. Exit the airlock. Outside, around the left from the other building's airlock, you can find armor shards and an adrenaline power-up. Re-enter the other building.

When you return to the main building, a zombie will drag Mark Ryan off toward the right as the airlock stalls, and then one of the evil souls possessing the soldiers will fly by you—or right through you—harmlessly. Kill the zombie, ascend the stairs, and open the door but then immediately step back - a zombie with a wrench will attack at point blank. You may notice that the right handrail is now damaged; it is possible to hop over it and crawl precariously along the pipes to find an item underneath the stairs. Head up the stairs and into the room with the bridge.

Kill the faceless zombie that was previously Ian Sinclair after it climbs up the ladder in front of you. If you try to return the way you originally came toward the right, the arm of a presently unknown creature will try to claw at you through it, breaking the doors. Instead, use the console at which Ian previously worked to extend the service bridge. A pistol Z-Sec will attack from an alcove on the right just past the bridge. Enter the door it was guarding.

Another pistol Z-Sec will take cover behind a crate. After dealing with it, go toward the left of the room and a zombie will approach from a crawl way. Search this room for the PDA of Frank Delahue in order to unlock the exit door. It is also possible to nab a med kit and some other supplies from the ledge above the zombie's crawl way by jumping off the nearby computer console. In the next room, a scientist calls for help from the platform above to the right, and you can kill the zombie as it approaches in order to save him. A second zombie is right around the corner to the right on your own level. Go through the door on the left.

Watch the floor, as it has exposed machinery, and falling into it is fatal. There is armor and a shotgun to the right, but it will activate an ambush which lowers the floor and triggers an attack by four zombies. There are med kits in the alcoves from which the zombies emerged in case they managed to do any damage. Climb the ladder to return to the higher level, and exit through the door in the left corner of the room. There are shotgun shells and armor shards immediately to your right in the next room.

Head down the corridor, and engage the Z-Sec and two zombies at the top of the stairs. A ladder to the left is available that will allow obtaining some items underneath the catwalk if desired. Walk backwards past the stairs and you will see a door open up on the left side of the room - engage the flanking zombie which attacks from this closet, and take the shells that are inside. Turn back forward to kill the other zombie approaching from ahead. There is more ammo on the shelf to your left, and a health station at the end of the corridor which you can use to heal.

Past the door is a cut scene which introduces a new enemy, the imp. Two shotgun blasts should be enough to destroy it. Note the area beyond the flaming gas jet, as it is possible to return here shortly for more items. Continue through the door. In the next room (this is the same room in which you earlier found the scientist calling for help, but you are now on the upper level) an imp is already coming around the corner. Kill it. You can enter the code 842 from Frank Delahue's PDA audio log into the first of the three screens along this catwalk to turn off the gas jet you just passed earlier - you can return there for the items on the other side if desired.

A zombie is right around the corner. At the end of the corridor, there is a zombie hiding behind a pillar with armor shards, and an imp will come from the area behind you. There is an already opened storage cabinet next to the stairs you just walked down which contains armor and a med kit. Continue along the platform overlooking the service bridge room and go through the next door. A health station to the left has 50 health. On the ground floor, there is an imp that jumps out violently from behind the first corner. It is followed by a zombie behind one of the pillars. Kill them and continue to the next room, where a shotgun Z-Sec will attack (it may have entered the room you were already in if you were not moving quickly enough).

There is nothing to be found in the plasma filter room. Continue to the left, as the door on the right was broken earlier by an imp. There is also nothing in the next curved room (Convergence Chamber 2), but an imp will perform a pouncing attack immediately after opening the door to exit from it. Move up to the door, and then quickly backpedal around the corner to avoid it. After defeating the imp, walk backwards into the next room.

A Z-Sec attacks from the convergence chamber you just left. Once eliminated, you can look at the storage cabinet with code 531 if you did not open it earlier. You will hear Scotty screaming in terror and pain inside the crawl way to the left. If approached, an imp will emerge and try to attack, so this area is better off avoided entirely. Proceed to Convergence Chamber 1, which is only a jump scare where a body will suddenly drop from the ceiling and a disembodied voice will be heard to say, "help me". The next room is where you previously met C. Rodgers, who regretted saying too much. An imp will break out of the stairs on the left as you approach them.

You should now be back in the crane room—an imp climbs from the rail on the opposite side, giving you ample opportunity to kill it using the explosive barrel nearby. When you approach the stairs, the crane will suddenly break, dropping heavy materials onto the stairs. Head up, and an imp will attack from the security checkpoint, which you should now enter (it was locked earlier).

Defeat the T. Brooks Z-Sec, who will come to life as you approach his former workstation. Heal from the health station if needed. Note that a Z-Sec will attack from the opposite side of the junction as you leave T. Brooks' station.

Head back to the elevator. One final imp will drop from the ceiling in the elevator room, and a pistol Z-Sec will be standing in the elevator itself when it opens. Kill them and then use the elevator panel to exit the level.

End-of-level secrets[edit]

Accessing T. Brooks' workstation in the security checkpoint allows unlocking two secrets:

  1. The other armament cabinet in the lobby outside can be opened, which allows access to the machine guns inside.
  2. A secret area can be unlocked across the chasm outside in the Underground Junction. The simplest way to reach that area is to go back to the exit out of the junction to the room where C. Rodgers died and look for a thin metal cable which stretches all the way across the chasm - play acrobat and tiptoe your way across to reach the previously locked chamber on the other side. It contains some early plasma gun ammo which will come in handy once you have reached the EnPro Plant.